99.9% SLA
Claude Sonnet 5.5: Model Introduction & Practical Guide
Claude Sonnet 5.5 is Anthropic's model for everyday coding, document creation and agent workflows. It combines visual understanding, adaptive reasoning and tool use with a 1,000,000-token context window and a standard output budget of up to 128,000 tokens.
Quick Facts
| Attribute | Value |
|---|---|
| Model | Claude Sonnet 5.5 |
| Developer | Anthropic |
| Positioning | Everyday coding, document and agent workloads |
1. Model Overview
Sonnet 5.5 focuses on practical work such as implementing a feature, investigating a bug or preparing a clear document. Anthropic positions it as a faster complement to Opus 5.5 for well-scoped assignments, with stronger communication and visual understanding than its predecessor.
2. Core Features
Software development. Work through feature requests, explain code and investigate defects.
Document creation. Draft reports, slide content and spreadsheet explanations.
Visual analysis. Interpret screenshots, charts and images alongside text.
Structured workflows. Combine tool use with schema-constrained output where the endpoint supports it.
3. Technical Specifications
| Specification | Detail |
|---|---|
| Context window | 1,000,000 tokens |
| Standard maximum output | 128,000 tokens |
| Input | Text and images; OpenRouter also lists file inputs |
| Output | Text |
| Reasoning | Adaptive by default |
| Effort levels | low / medium / high / xhigh / max |
| Default effort | high |
| Knowledge cutoff | June 2026 |
4. Capability Comparison
Within the Claude 5.5 family, Sonnet balances speed and capability for daily work. Haiku targets faster repetitive tasks, while Opus is intended for more complex, open-ended work. Compare the models using the same source material and acceptance criteria.
5. Core Advantages
Visual input, a large context window and structured results let a single workflow move from source review to a draft or proposed fix. Effort can be tuned to the task instead of treating every request as equally difficult.
6. Recommended Use Cases
Feature implementation, defect investigation, report drafting, presentation outlines, spreadsheet analysis and screenshot review.
7. Example Prompts
Coding: "Review this diff against the acceptance criteria. Identify the smallest correction and propose a regression check for the defect."
Documents: "Turn these notes into a decision memo. Separate confirmed facts, assumptions and unresolved questions, preserving the source references."
8. Selection Recommendations
Provide a concrete deliverable and a way to judge it. For a tool-driven workflow, use automatic tool selection and check the resulting action. When migrating, replace fixed thinking budgets with effort controls and inspect responses by content-block type.
Sources & Further Reading
Specifications checked on November 5, 2026.
